USE OF FERROELECTRIC HYSTERESIS PARAMETERS FOR EVALUATION OF NIOBIUM EFFECTS IN LEAD-ZIRCONATE-TITANATE THIN-FILMS

The effects of niobium doping on the hysteresis parameters of sol-gel Pb-1.1-x/2(Zr0.53Ti0.47)(1-x)NbxO3 (0 < x < 0.05) have been reported f br two sets of films with analogous grain size and degree of (111) tex ture but with different surface microstructures. For both sets, a stro ng continuous decay of the remnant and maximum polarizations and slope of the hysteresis loop at the coercive field was observed with increa sing niobium concentration. The held dependence of the remnant polariz ation for any given niobium-doped him was identical to the functional field dependence of the undoped reference him, if multiplied by a niob ium-concentration-dependent constant. Although the maximum and remnant polarizations decayed as the dopant level increased, their difference remained the same value as that of the undoped him at any given field . The width of the loop (at zero polarization) was insensitive to the niobium concentration at any given held, A linear increase in coercive held asymmetry (up to 40 kV/cm) was observed with niobium addition, y et was field independent and, thus, electrostatic in origin. Niobium g overned switching through a reduction of the number of switching domai ns, without changing the total lattice polarization response. Microstr ucture-related effects on switching, such as decreased volume fraction of ferroelectric material or field-screening effects due to the prese nce of a pyrochlore second phase, were eliminated as the origin of the hysteresis changes. This paper has demonstrated how hysteresis featur es and their field dependencies can be used to separate the effects of niobium-induced microstructural changes from niobium lattice doping i nfluences on the hysteresis loops.